Oscillator with free piston



Nov. 23, 1965 E. A. THOMPSON OSCILLATOR WITH FREE PISTON Original FiledJuly 12. 1961 12 Sheets-Sheet l INVENTOR.

EARL A, THOMPSON A TTORNEV Nov. 23, 1965 E. A. THOMPSON OSCILLATOR WITHFREE PISTON 12 Sheets-Sheet 2 Original Filed July 12. 1961 INVENTOR.EARL A. THOMPSON BY M r, A M

ATTORNEY Nov. 23, 1965 THOMPSON 3,218,760

OSCILLATOR WITH FREE PISTON Original Filed July 12, 1961 12 Sheets-Sheet3 x l 4 I20 /42 /08 11s H4 I24 94 9s FIG. 4

INVENTOR. gARL A. THOMPSON ATTORNEY Nov. 23, 1965 E. A. THOMPSON3,218,750

OSCILLATOR WITH FREE PISTON Original Filed July 12, 1961 12 Sheets-Sheet4 IN VEN TOR.

A TTORl/EV Nov. 23, 1965 E. A. THOMPSON OSCILLATOR WITH FREE PISTON 12Sheets-Sheet 5 H 70 l58 H i l V [7O I: I i d w i g 5 4 F1 G. 9 INVENTOR.

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5AM A. THOMPSON @A if M m ATTORNEY Nov. 23, 1965 E. A. THOMPSON3,218,760

OSCILLATOR WITH FREE PISTON Original Filed July 12, 1961 12 Sheets-Sheet7 W I O INVENTOR.

Fla 1'] 5ml A. THOMPSON ATTORNEY Nov. 23, 1965 E. A. THOMPSON 3,218,760

OSCILLATOR WITH FREE PISTON Original Filed July 12. 1961 12 Sheets-Sheet8 A ?Z4 (Q) P I 6, [Z r V N INVENTOR.

gA/QL A THOMPSON ATTORNEY Nov. 23, 1965 E. A. THOMPSON OSCILLATOR WITHFREE PISTON 12 Sheets-Sheet 9 Original Filed July 12. 1961 FIG. /5

F] G. 14 INVENTOR.

EARL A. THOMPSON ATTORNEY Nov. 23, 1965 E. A. THOMPSON OSCILLATOR WITHFREE PISTON l2 Sheets-Sheet 10 Original Filed July 12. 1961 \O I w?INVENTOR. gfIRL A. THOMPSON ONW E. A. THOMPSON OSCILLATOR WITH FREEPISTON Nov. 23, 1965 Original Filed July 12, 1961 12 Sheets-Sheet 11INVENTOR.

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EARL ,4. THOMPSON ATTOR/VB United States Patent 3,218,760 OSCILLATORWITH FREE PISTON Earl A. Thompson, Oakland County, Mich.

(1300 Hilton Road, Ferndale, Mich.) Continuation of application Ser. No.123,578, July 12, 1961. This application July 28, 1964, Ser. No. 386,12028 Claims. (Cl. 5150) This application is a continuation of myapplication Ser. No. 123,578, filed July 12, 1961, now abandoned.

This invention relates to machine tools and more particularly toimproved oscillator apparatus for imparting to-and-fro motion to ashiftable member on a machine tool, such as a slidable wheel carriage ona grinding machine.

The problem of obtaining a highly finished surface on a metal workpieceby means of a grinding wheel depends upon the quality of the surface ofthe wheel. A slightly raised particle of grit or other irregularity onthe working face of the wheel, if constantly rotating in one plane, willcause an indentation scratched in the surface of the workpiece. Toovercome this undesirable result, an oscillatory axial motion of thegrinding wheel is often employed to prevent repetitious engagement ofirregularities between the wheel and the workpiece and to erase suchundesirable grooves as they are formed during the grinding operation. Inaddition to the to-and-fro motion during the grinding operation, it isoften desirable to move the wheel to and fro during the dressingoperation but with a different stroke and at a different speed.Apparatus heretofore available for these operations is ordinarily eitherundesirably complex and subject to frequent malfunction or is sointimately incorporated in the grinding machine that alterations arerendered prohibitive.

Especially on internal grinding machines-in relation to which thebroadly usable elements of this invention are disclosedare theseproblems encountered. On an internal grinder, where a small diametergrinding wheel rotating at high velocity and supported upon a relativelyheavy carriage must be moved endwise through a long stroke into anaperture in a workpiece and later returned with positive control in bothdirections, and moved radially to grind the work when in the forwardposition while being oscillated through a short endwise stroke to finishthe work surface, the wheel carriage must be shifted through the longstroke at a high speed, reciprocated through the short stroke at aslower speed, and reciprocated against a retruing tool through adifferent stroke at yet another controlled speed. The complexity ofthese motions, coupled with weight problems and space limitations onmodern grinders, intensify the above problems.

Accordingly, it is an object of the present invention to provideimproved apparatus for imparting oscillatory motion especially suitablebut not limited to a relatively massive shiftable carriage member on amachine tool.

Another object of the invention is to provide improved apparatus forimparting to-and-fro vibratory motion to a shiftable carriage which maybe located remote from the carriage at any convenient location on ornear the machine.

A further object of the invention is to provide improved apparatus whichmay selectively impart one of two different oscillatory motions to acarriage and which may be used in addition to other mechanism which alsoshifts the carriage with positive control in both directions and withyet a different motion.

A further object is to provide, in a machine tool such as an internalgrinder, improved oscillating apparatus of the mechanico-hydraulicvariety including rotary cam actuated transmitters for selectivelytransferring motion through liquid columns to the shiftable carriage onthe 3,218,760 Patented Nov. 23, 1965 machine and which works against acorrespondingly selectively introduced counter-biasing force.

A further and more particular object is to provide, in combination witha carriage shiftable by opposed, cooperating rotary cam powered andcontrolled hydraulic pulsators, a means for imparting additionalshifting motion to the carriage which includes a third hydraulicpulsator operable against a constant pressure returning source whereinthe returning source fluid is isolated from the working fluid of thehydraulic pulsators.

Further objects and advantages of the present invention will be apparentfrom the following detailed description, with reference to theaccompanying drawings in which like reference characters refer to thesame parts throughout the several views, and in which:

FIGURE 1 is a perspective view of an internal grinding machine embodyingthe features of this invention;

FIGURE 2 is a side elevation of the machine shown in FIGURE 1, as seengenerally from the front of FIG. 1;

FIGURE 3 is an end view on an enlarged scale of a portion of the machinelooking from line 33 of FIG- URE 2;

FIGURE 4 is a sectional view along line 44 of FIG- URE 3 showing thefluid motor for actuating the lead screw feed arrangement for theparallel link supported work carrier;

FIGURE 5 is a longitudinal sectional view along line 5-5 of FIGURE 6showing the lead screw feed arrangement for advancing the dresser slide;

FIGURE 6 is a composite sectional view along line 6-6 of FIGURE 5 andline 66 of FIGURE 7 showing the worm shaft for actuating the lead screwfeed arrangement;

FIGURE 7 is a sectional view along line 77 of FIG- URE 6 showing thefluid motor actuated ratchet mechanism for controlling the worm shaft toautomatically advance the dresser slide;

FIGURE 8 is a plan view, with parts broken away, of the dressingapparatus;

FIGURE 9 is a sectional view along line 99 of FIG- URE 8 showing thefluid motor for moving the dressing apparatus between its operative andinoperative positions;

FIGURE 10 is a sectional view showing the three spaced point supportarrangement for the wheel carriage, and the fluid motor for shifting thecarriage in relation to its supporting frame;

FIGURE 11 is a sectional view along line 11-11 of FIGURE 10 showing theroller supports for the wheel carriage;

FIGURE 12 is an elevational view of the reservoir housing of theoscillator mechanism of this invention;

FIGURE 13 is a sectional view along line 13-13 of FIGURE 12 showing theinterior of the reservoir housing;

FIGURE 14 is a sectional view along line 14-14 of FIGURE 16 showing thegearing arrangement for driving the two worm shafts of the oscillatorapparatus from the single input drive shaft;

FIGURE 15 is a sectional view along line 1515 of FIGURE 16 showing thecamshaft and cams and other aspects of the interior of the oscillatorapparatus;

FIGURE 16 is a partial elevational view with parts broken away of theoscillator mechanism of this invention;

FIGURE 17 is a sectional view along lines 1717 of FIGURE 13 showingdetails of the free piston assembly in the oscillator reservoir housing;

FIGURE 18 is a view in schematic fashion of the plural speedtransmission with its electrical and hydraulic controls for themechanico-hydraulic motivator used by the machine of this invention; and

FIGURE 19 is a view in a schematic fashion of a. mechanico-hydraulicmotivator and the free piston oscil- 3 later of this invention combinedfor application to an internal grinding machine.

Looking at FIGURES 1 and 2, the internal grinding machine which embodiesthe features of this invention comprises a generally rectangular basefor movably supporting compound slide rests, to be explained, andprovided with suitable leveling means 12 for supporting the entiremechanism on a floor. A mechanico-hydraulic drive unit comprising a baseassembly 14 and a plural speed transmission 16 powers a main camshaft236 (FIGS. 2, ll, 19) which may extend from either side thereof andthrough the length of the base 10 to drive rotary cams in at least twocam housings 18, 18 (all to be later described) supported on oppositeends of the base 10 and protruding therefrom in a convenientlyaccessible fashion. A housing may be provided for electrical controls,and a platform 17 located interiorly of the base 10 may be provided tosupport the oscillator apparatus of this invention.

As'shown in FIGS. 2 and 3, at one end of the base 10, there is a bed 20having suitable guideways 22 on the upper portion thereof, which extendhorizontally at right angles to a centerline of the machines base. Thissupports a slide member 26 having mating guide elements 28 for slidingmotion crosswise of the machine. An extension 30 of the bed 20 (FIG. 3)supports a fluid motor actuated ratchet mechanism 32 for rotating a leadscrew 34 connected to the slide member 26 to move it to and fro on theguideways 22.

A work feeding carrier 36 is supported for to and fro motion upon theslide member 26 by means of a parallel link anti-friction arrangement.Four generally vertical links 38 support the work feeding carrier 36above the slide member 26 near its four corners; the links 38 arepivotally mounted at each end in either slide to form therewith twinparallelograms, each in a vertical plane extending crosswise of thelongitudinal dimension of the machine base. 'The front two links and therear two links are each interconnected by, and made unitary with, a bar(not specifically shown) having qualities of resistance to torsionalforces sufficient to insure precise parallelism between each pairv oflinks. A series of limit switches 400, 402 and 404 may be provided todetect different positional relationships between the base and thedresser carrier 26.

Supported on an extension 40 of the slide 26 is a feed mechanism 42 forimparting limited arcuate motion to the carrier 36. The feedarrangements 32 and 42 are both lead screw feeders actuated by fluidmotors. The ratchet feed mechanism 32 is disclosed in detail in FIG URES5, 6 and 7. Lead screw 34 which is threadedly connected to the slide 26extends into the housing 44 of the ratchet mechanism which is attachedto the extension 30 of. the base slide 20. A crank 46 rigidly secured toa cross shaft 48 including a worm 50 engaging a worm wheel 52 keyed onlead screw 34 serves to rotate the lead screw, as can be understood fromFIGURES 5 and 6.

Secured also on cross shaft 48 is a toothed rotary ratchet 54 which mayalso be utilized to rotate the shaft 48 and in turn automaticallyactuate the lead screw 34. Mounted concentrically of the shaft 48 forfree rotation thereabout is an oscillating member 56 which pivotallysupports a pawl 58 and a spring 60 which urges the point of the pawlinto working engagement with the teeth of the rotary ratchet 54.Oscillating member 56 also has an apertured ear 62 snugly engaged by apin 64 fastened in a cut-out area 66 of a shiftable piston 68. Thepiston 68 shifts to and fro within a cylinder 70 having connections 72,74 for admitting pressurized fluid to either end thereof. Adjustablelimit stops 76 at either end of the cylinder 70 serve to closely controlthe stroke of the piston 68. A dowel pin 78 fixed in the housing 44serves to lift the point of the pawl 58 out of locking engagement .withthe rotary ratchet 54-when the piston 68 is at the extreme lower end(FIGURE 7) of the cylinder 70 against the limit stop 76 to enable thecross shaft 48 to be rotated in either direction by the hand crank 46.Pressurized fluid admitted to the lower end of the cylinder 70 throughconnection 74 will shift the piston 68 upwardly and oscillate the member56 clockwise to move the pawl 58 and consequently the ratchet 54 and itsassociated cross shaft 48 through several degrees of angular motion.Rotation of cross shaft 48 in turn actuates lead screw 34 through aclosely controlled amount of rotation to move the slide 26 in relationto the bed 20 of the machine.

The feeder mechanism 42 actuates a traveling lead screw 80 connected tothe work carrier 36 in a manner which allows for limited up and downmotion to compensate for the arcuate movement of the carrier 36 as itpivots on links 38 to and fro in relation to the slide member 26. Keyedagainst axial movement about lead screw 80 is a rotary nut 84 havinggear teeth 86 around its periphery which are adapted to be engaged onopposite sides by racks 88 associated with a pair of lash free pistons90, 92 shift-able in opposite directions in a pair of parallel cylinders94, 96, respectively. Fluid under pressure admitted to the uppercylinder 94 through a connection 98 moves the piston to the left (andlower piston 92 the same distance to the right), and oil for rotatingthe nut 84 in the other direction is admitted through a connection 100to the lower cylinder 96 to move the lower piston 92 to the left (andupper piston 90 back to the right). An adjustable stop 102 limits therightward stroke of piston 90 which in turn determines the length of thefeed movement of the carrier 36.

Attached to the left end of upper cylinder 94 is a diamond wearcompensator 108. The compensator comprises a limit stop or abutment forthe upper piston 90 of motor 42, which is adjustable by means of anenlarged thread portion 112 thereon having threads which mate withsimilar threads on a fixed stepped sleeve insert 114 which also containsa cylinder 116 of the same diameter as cylinder 96, and is itselfcontained within a housing 118 secured to the housing for the motor 42.A manually turnable handle 120 on the outer end of the adjustable limitstop shaft serves to move it in and out to determine the stroke of thepiston 90 in the cylinder 94 to change the rest position of thearcuately movable carrier 36 in relation to the slide member 26.

Loosely received on the limit stop 110 is an apertured free piston 122which slides in the cylinder 116 when the enlarged screw thread portion112 of the limit stop is screwed inwardly toward piston 90. A connection124 admits fluid communication with one end of the cylinder 116, andanother connection 126 admits pressurized fluid to the other endthereof, both in a manner later to be described. When the limit stop 110is fully retracted to allow a maximum stroke of piston 90, the enlargedscrew thread portion 112 looks the piston 122 against sliding; however,when limit stop 110 is moved in the other direction to limit the strokeof piston 90, the piston 122 will be freely movable for an equivalentdistance to vary the volume of the chamber 116.

Mounted on a swivel plate 130, which may be fixedly secured in a desiredposition on the carrier 36 by suitable means such as a bolt 132, is awork holder and a dressing apparatus. The work holder 133 comprises acollet or chuck which may grip or ungrip work pieces and eject finishedwork pieces with mechanism powered by fiuid motors, not shown, enclosedwithin the collet housing. The collet may be rotated by a belt 134driven from a motor 136 also mounted on a swivel plate 130.

The dressing apparatus 138 is shown in detail in FIG- URES 8 and 9 andcomprises a retruing tool such as a diamond point 140 fixedly mounted onan arm 142. The arm is pivotable about the axis of a shaft '144 betweentwo positions: one an operative position, and the other an inoperativeposition. The arm 142 is keyed at 146 to the shaft 144, and the shaft144 has gear teeth 148 therearound which mesh with the teeth 150 ofopposed racks made integral with alternately reciprocable pistons 152slidably received within parallel cylinders 154. Oil pulsed through aconnection 156 to the lower of the cylinders 154 moves the lower piston152 to the right (FIGURE 9) and pivots the diamond arm 142 upwardly tothe inoperative position. Fluid under pressure admitted through aconnection 158 to the left hand end of the upper of the cylinders 154moves the upper piston 152 to the right, and the lower piston back tothe left, to pivot the diamond arm 142 downwardly and hold it in theoperative position determined by a suitable arm-engaged limit stop (notshown) on the swivel plate 130, as can be understood.

The stroke of the upper of the pistons 152 is limited by an abutment 160secured to a large area piston 162 reciprocable in a cylinder 164. Oiladmitted through a connection 166 by means later to be described servesto shift the large piston 162 and its associated limit stop 160 to theright to hold the diamond arm down in the operative position.

Attached also to the swivel plate 130 is a tooling plate 170 upon whichsuitable mechanism (not shown) may be mounted for moving a new workpiece from a supply source such as a loading chute to the collet holder133, and then removing the finished work piece from the collet anddepositing it in an unloading chute or other suitable dischargemechanism. It will be understood that any suitable loading and unloadingmechanism may be utilized depending upon the size or configuration ofthe work piece to be internally ground.

Thus it will be seen that the work piece chucked in the work holder 133has several motions in relation to the base 10. First, there is thedress compensating motion transverse to the horizontal centerline of themachine which is accomplished by the slide member 26 moved by the leadscrew arrangement 34 under control of the automatic ratchet mechanism 32or the hand crank 46. Secondly, there is an arcuate work feed motion ofthe work holder 133 about the lower extremities of the parallel links 38which is also movement about a line parallel to the base centerline;this motion is extremely limited and approaches a short horizontalmovement. It is accomplished automatically by fluid motor actuated leadscrew 80 in conjunction with the anti-lash fluid motor arrangement 42.The chucked work piece is also rotated by means of the motor 136 duringgrinding operations. The wheel dressing apparatus 138 is positioned in afixed location with respect to the chucked work in what is oftenreferred to as a diamond sizing arrangement.

Positioned on the other end of the base 10, juxtaposed to the workcarrying arrangement just described, is a framework 172 which supports atool such as a grinding wheel for to and fro motion along a lineparallel to the machine centerline. Fixedly positioned on the frame 172is an upper guide bar 174 parallel with the longitudinal axis of themachine for guiding the movement of a grinding wheel carriage. On thelower portion of the frame 172 are two opposed bores 176 axially alignedin a direction also parallel to the longitudinal axis of the machine andoccupying with the upper bar a plane which is parallel to the axis ofthe machine and inclined approximately half-way between the vertical andthe horizontal.

Inserted within each bore 176 is a sleeve-like insert 178 with parallelroller tracks accurately machined lengthwise therein. One roller trackhas its bottom roller supporting face 180 lying normal to the singleinclined plane in which the axes of the guide bar 174 and the two bores176 lie. The other roller track in each sleeve insert has its rollersupporting face 182 lying in a plane parallel to the plane in which theguide bar and the aligned bores lie (FIG- URE 11). Freely rollable ineach track of each sleeve insert are rollers 184 spaced by suitableretaining cages 186. The rolls 184 are thus arranged in the differenttracks with their axes extending normally in V fashion.

6 Supported on the rollers 184 is a slide bar 188 free to move axiallyto and fro on the rolls which will in turn roll to and fro in theirtracks within the bores. Slide bar 188 is surrounded, at a locationintermediate its ends, by a wheel carriage 190 which is rigidly clampedthereto by suitable bolts 187.

The upper end of the carriage 190 surrounds the guide bar 174 by meansof another sleeve-like or tubular insert 192 having an internaldimension somewhat larger than the diameter of the bar 174 andcontaining a single rollerway 194 extending lengthwise along theinternal surface thereof. Rolling in the track 194 are rollers 196 in asuitable cage 198 for supporting the upper portion of the carriage 190on the guide bar 174 and preventing gravity urged pivotal motion aboutthe axis of the roller slide bars 188. The axes of the rollers 196extend parallel to the plane in which the bars 174, 188 lie. Thus, asthe carriage 190 is moved to and fro the upper portion of the carriagerolls on rollers 196 along the guide bar 174 fixed in the frame 172, andthe lower portion of the carriage 190, which comprises the slide bar188, rolls on the rollers 184 in the axially aligned bores 176 in theframework. The carriage 190 is moved to and fro on the rollers by afluid motor 200, attached to the framework 172 and comprising a cylinder202 containing a piston 204, the rod 206 of which is rigidly attached at208 to the wheel carriage 190. Fuid under pressure admitted through aconnection 210 will move the piston 204 to the left in its cylinder 202and consequently move the wheel carriage 190 (including its guide bar188) to the left. Fluid admitted through connection 212 at the other endof cylinder 202 will move the wheel carriage oppositely, as can beunderstood. One portion of the piston rod 206, enlarged by means ofsleeve 214 to form an abutment portion, limits the stroke of the piston204 by contact with an adjustable stop member 216 in the cylindersurrounding the rod 206. Suitable means such as a rotating nut 208turned by suitable worm mechanism from the exterior of the housing ofthe motor 200 may be utilized to adjust the position of the limit stop216.

Mounted on the wheel carriage 190 is an internal grinding wheel 220supported for high speed rotary motion by a spindle 222 rotatably drivenby suitable mechanism such as a high speed turbine 224, which in turnmay be powered by fluid from a remote source. Such a source may comprisea pump unit 226 driven by a suitable motor which builds up a pressurehead in turbine fluid and pumps it through a line 228 to the turbine,and returns fluid through a similar line 230 to the pump. This resultsin a very high speed drive for the wheel which, because of the flexiblehoses 228, 230, does not require that a cumbersome power unit for thegrinding wheel be positioned on the carriage 190 itself.

For the purpose of giving coordinated motivation to the various fluidmotors described above, there is provided a mechanico-hydraulicprogramming system for repeatedly producing a cycle of programmedmovement, illustrated schematically in FIGURES l8 and 19. This systemmay be constructed as a unit having its own housing which may bepositioned at any convenient location on or adjacent the base 10 andconnected to the various hydraulic cylinders by suitable rigid orflexible piping. The mechanico-hydraulic drive unit comprises a mastercamshaft 236 carrying a plurality of cams 238, the followers of whichoperate transmitter pistons 240, each of which forms part of anexpansible chamber liquid column type motion transfer device of whichthere are nine units or sections shown in the diagram of FIGURE 19. Eachpiston reciprocates in a cylinder 242 having a head B which contains asuitable inlet replenishing check valve 308 and a high pressure reliefvalve 310, both of which communicate with a low pressure oil reservoir312 which may be formed in a housing enclosing the drive unit.

For turning the camshaft 236, a motor 246 drives an input shaft 248 ofthe two speed transmission 16 through a belt drive 250, as clearly seenin schematic FIGURE 18. The input shaft 248 drives a pinion 252 and alsotheinput member of a hydraulically engaged, spring released clutch 254.Pinion 252 drives a gear 256 secured to a countershaft 258 which carriesa pinion 260 at its opposite end. Pinion 260-drives a gear 262 andtherewith constitutes a set of change speed gears. Gear 262 drives theinput member of a second hydraulically engaged, spring released clutch264. The driven members of clutches 254, 264 are secured to the oppositeends of a shaft 266 having a worm 268 thereon and a brake drum 270. Thelatter has a spring biased hydraulic motor 272 for engaging the brake.Worm 268 drives a worm wheel 274 secured to the master camshaft 236, thecamshaft being visible in both of FIGURES 18 and 19.

For the purpose of automatically controlling the starting, stopping, andspeed of the transmission, there is provided a hydraulic control pump276 driven from the gear 262, which may circulate a body of oilcontained in the housing surrounding the transmission. The pump 276 maydeliver to a combined accumulator and relief valve comprising a springloaded piston 278 and also supplies oil to a bank of control valves 280,282 and 284. In the FIGURE 18 diagram, each valve is shown as atwo-position valve, spring biased to the position illustrated in whichthe connections shown in the cross-hatched rectangles are established.Single headed arrows are used to indicate flow at reservoir pressuresand double headed arrows to indicate flow at pump delivery pressure.Each of the valves, when shifted, establishes the connections shown inthe unhatched rectangles immediately below the hatched rectangles.

Valve 280 is arranged to be shifted by a solenoid 286. Valves 282, 284are arranged to be shifted by the adjustable cams 288, 290 respectively,which are positioned on camshaft 236. In addition, the valve 282 has ahydraulic holding cylinder 292, which holds the valve 282 in its shiftedposition until it is released by the shifting of valve 284. Valve 280 inthe position shown delivers pressure fluid to engage the brake 272 andalso exhausts fluid to release the low speed clutch 264. When shifted,valve 280 exhausts fluid to release brake 272 and supplies pressurefluid to engage the low speed clutch 264, subject, however, to aconjoint control by the valve 282.

The latter valve, in the position illustrated, exhausts fluid to releasethe high speed clutch 254, and places the low speed clutch 264 under thecontrol of valve 280. In its shifted position, valve 282, provided valve280 has been shifted, delivers pressure fluid to engage high speedclutch 254 and exhausts fluid to release low speed clutch 264. Aspreviously explained, the valve 284 is merely a reset valve forby-passing the holding cylinder 292 to permit valve 282 to return to itsspring-biased position shown in the drawings.

Thus, energization of solenoid 286 will start the camshaft 236 rotatingat slow speed, and later the cam 288 will shift the transmission todrive the camshaft at high speed, and still later the cam 290 will againshift the transmission to slow speed. So long as the solenoid 286remains energized, the camshaft 236 will continue to rotate, first at aslow speed and then at a high'speed during each revolution controllingits own speed changes by operation of the cams 288 and 290.

For the purpose of controlling the drive motor 246 and solenoid 286,there is provided an electric control circuit connected between a pairof electric supply lines designated L1 and L2. The circuit may include amaster relay 294 of the holding type having a manual master start switch296 and a manual master stop switch 298. Relay 294 controls the motor246 and also a cycle control relay 300 of the holding type having amanual cycle start switch 302 and a manual cycle stop switch 304. The

normally opened contacts of relay 300, which are of themake-before-break type, control energization of cycle sole- .noid 286directly. The normally closed contacts of relay 300 also controlsolenoid 286, but are in series with a cam switch 306 on the camshaft236 and arranged to be opened once during each revolution thereof. Thearrangement is such that when the cycle stop switch 304 is operated atany point in the rotation of camshaft 236, relay 300 will bede-energized, but solenoid 286 will remain energized until cam switch306 opens at the predetermined stopping point. Operation of the masterstop switch 298, however, will de-energize solenoid 286 immediately,regardless of the point in the cycle and will also de-energize motor246.

The camshaft 236, as previously mentioned in connection with FIGURE 19,drives a number of cam operated hydraulic pulsator sections designated athorugh i inclusive, and shown diagrammatically on the left portion ofFIGURE 19. Each section may comprise units duplicating the single actingpulsating cylinder 242, the head B of which contains the replenishingcheck valve 308 and the spring closed relief valve 310. All thereplenishing and relief valves are connected to a common oil reservoir312 formed for instance in the housings 18, 18 of each unit. Thereservoir 312 is preferably subjected to a low, yet super-atmospheric,pressure by a body of compressed air or other pressure maintainingarrangement. Check valve 308 allows flow from the reservoir 312 to thecylinder 242, while relief valve 310 allows flow oppositely when thecylinder pressure exceeds a certain value. Thus, each of the pairs ofvalves 308 and 310 may be referred to as a balancing valve and serve tobalance the volume of fluid in each of the liquid column sections, aswill be later described.

The pulsator section a is connected by a closed liquid column line 314awith the upper cylinder 154 of the fluid motor which moves the diamonddressing arm 142 between the operative and inoperative positions. Thepulsator section b connects by a closed liquid column line 3141: withthe diamond compensator unit 108 through connection 126 to impart motionto the compensator piston 122 when it is free to move. 'Pulsator sectiond connects by means of a liquid column 314d with the connection of thecylinder 96 of the fluid motor 42 which imparts limited arcuate motionto the parallel link supported carrier 36; line 314d also extends toconnection 124 of the compensator apparatus 108 for conveying surplushydraulic fluid from the compensator cylinder 116. Pulsator section 1 isconnected by a closed liquid column 314 with the ratchet feed mechanism32 for imparting motion to the slide member 26. Pulsator section g isconnected by a liquid column 314g with the connection 212 at one end ofthe motor 200 for moving the wheel Carri-age away from the work holder133 on the frame 172; pulsator section i is connected by a liquid column314i with the connection 210 at the other end of the motor 200 inopposition to the section g to move the wheel carriage 190 toward thework holder 133. Pulsator section 0 may connect by means of a flexibleline 314a with the work piece holder 133 for actuating the work piecegripping collet; similarly, pulsator section e may be connected by aline 314e with the holder 133 for ejecting a finished work piece uponcompletion of the grinding operation. Pulsator section it connects bymeans of a liquid column 314]: with a hydraulic valve 370 for actuatingthe same for a purpose later to be described. Other pulsator sections,not shown, on either end of the shaft 236, may be utilized for operatingvarious tooling mounted on the upright plate for loading work pieces toand unloading them from the holder.

In order to insure proper synchronization of the driving and drivenelements -of each pulsator section, it is desire able to provideslightly more fluid displacement in the driving or transmitting elements240, 242, than is present in their respective fluid motors at theopposite end of the liquid column line. Thus, at the end of eachadvancing stroke of the transmitter piston 240, a small amount of fluidwill be discharged to reservoir 312 through the relief valve 310. Thisamount plus any amount lost through leakage will be returned to theliquid column at the end 9 of the return stroke by the operation of thereplenishing valve 308. The amount blown over the relief valve atsection b will depend upon the amount of movement allowed piston 122.

In FIGURE 19 there are shown several circles marked R connected to theend of the hydraulically operated valves and some of the motivecylinders opposite the liquid column connections. These symbolsdesignate the return oil connections by means of which a pulsator systemmay be hydraulically biased so as to maintain the follower in closecontact with the cam as the falling portion of the cam contour recedesfrom the follower. This bias is maintained by a high pressureaccumulator or oil reservoir, not shown, which may be provided with amanifold whereby all of the R0 connections are joined together and tothe high pressure reservoir. The showing of separate return oilconnections in FIGURE 19 is indicative of any suitable type of biasingpressure source comprising a single common accumulator. The contours ofall the individual cams 238 are likewise not illustrated in specificdetail since they may be formed in accordance with the usual practice tocause motivation of each of the respective hydraulic motors and thevalve 370 in accordance with the particular operating cycle desired forthe machine.

It will be noted that there is no RO connection with the fluid motor 200for shifting the wheel carriage 190, the motor 200 being actuated by theopposed hydraulic pulsators g and i of the program motivator. The twocams at these two stations are designed with generally complementarycontours whereby the cam at section g moves the piston 204 away from theforward stop 216 and the cam at section 1' moves the piston back towardthe stop 216. The cam that is not thus shifting the carriage presents afalling face to its follower to allow retraction of the liquid columnfrom the moving piston 204. By means of this double cam arrangement, arelatively heavy wheel carriage may readily be shifted with positivecontrol in both directions because the powering pulsator must overcomeonly the inertia of the carriage plus the relatively low pressure of therefill reservoir 312, and need not also overcome the relatively highpressure of the counter-biasing fluid from the source RO. Furthermore,the piston 204 may be held against a limit stop at either end of itsstroke, by means of a slight cam rise which will divert liquid to thereservoir 312, with a force determined by the setting of the springforce for the relief valve 310 associated with the holding cam.

The oscillator unit 320 of this invention (FIG. 2), as previouslymentioned, may be mounted on an appropriate ledge 17 within the base ofthe machine, or at any other location adjacent or remote from themachine, as desired. The unit consists of a generally rectangular casthousing 322 which may support on its top an enclosed reservoir 324 for asupply of hydraulic fluid maintained at low, super-atmospheric pressure,and a drive motor 326. A belt drive 328 including suitable pulleys maytransfer rotary motion from the drive mot-or 326 to an input drive shaft330 (FIG. 16) extending through and journalled in the housing 322 of theoscillator unit.

Within the housing of the oscillator unit, as best seen in FIGURES 14,and 16, the drive shaft 330 serves to impart rotary motion at differentspeeds to two separate camshafts. A pair of drive pinions 332 and 334,keyed on one end of the input shaft 330 outside the confines of thehousing 322 and Within a cover plate 336, rotate a pair of countershafts338 and 340. The shaft 338 is driven from the pinion 332 through aspacing and direction reversing idler pair 342 and a pinion 344 keyed onthe shaft 338 and meshing with the idler. The shaft 340 is driven fromthe drive pinion 334 directly through a pinion 346 keyed on the end ofthe shaft.

The parallel countershafts 338, 340 have worms 348, 350 keyed thereon ina position to mesh with worm gears 352, 354 secured to the parallelcamshafts 356, 358,

respectively, which extend parallel to one another in a horizontal planeand lie in vertical planes normal to the countershafts. The shafts 356and 358 are journalled at 360 (FIG. 15) near their ends in the housing322 of the oscillator unit. As shown in FIG. 15 and 19 the wheeldressing camshaft 356 has a pair of rotary cams 362 and 364 keyedthereon within the housing 322; and grinding oscillating camshaft 358has a single cam 366 keyed thereon for rotation in a direction oppositeto the cams 362, 364 and at a dilferent rate of rotation.

Each of the three cams operates a roller type follower mechanicallylinked to a piston reciprocable in a cylinder formed within the top ofthe housing 322 of the unit, as can be seen. Each follower, piston andcylinder combination forms a liquid pulsator similar to the pulsatorsections a through i operated by the cam 238 on the camshaft 236 of themechanico-hydraulic motivator for the grinding machine without, however,including balancing valves. The three pulsator sections x, y and z ofthe oscillator are similarly connected by liquid columns to suitablevalves and thence to the grinding machine.

Grinding pulsator section x operated by cam 366 connects by -a liquidcolumn 368x (FIG. 19) with the rod end connection 212 of the motor 200which retracts the wheel carriage on the fixed frame 172 (see FIGURE19). A suitable fluid pressure responsive three position valve 370interrupts the liquid column 368x. The valve in the normal (crosshatched) position determined by pressure from the source R0 diverts theliquid column through a line 372 to the low pressure reservoir 324. Thevalve 370 is adapted to be shifted by a liquid column from pulsatorsection h of the main motivator unit to establish the connections in theuppermost of the three rectangles. With the valve thus shifted by thepulsator section 71, the liquid column 368x extends directly from thepulsator section x of the oscillator to the rod end of the fluid motor200 so that the wheel head is now oscillated for grinding by the cam366. When the cam 238 at pulsator section h of the main motivator unitpresent a falling face to its follower to allow the valve 370 to againshift back toward the normal position to establish the connectionsillustrated in the lowermost (cross-hatched) rectangle, a momentarydwell 370' on the cam h allows the valve 370 to establish, for a shorttime, the connect-ions illustrated in the middle rectangle wherebyexcess fluid in the column 368x is permitted to drain back to thereservoir 324, as can be seen.

Work feed actuator section y operated by cam 364 of the oscillator unitconnects by means of a liquid column 368y with the ratchet lead screwadvancing mechanism 32 which serves to move the work holder and thedressing apparatus radially to and from the grinding wheel. A fluidpres-sure responsive valve 374 also interrupts liquid column 368y and,in the normal RO biased (cross-hatched) position, diverts the liquidcolumn through a line 376 to the low pressure reservoir 324. Valve 374is adapted to be shifted by means of fluid pressure from a line 378 to aposition in which the connections illustrated in the uppermost of thetwo rectangles are established. In this position, the liquid column 368yextends in uninterrupted fashion between the pulsator y and the ratchetfeed mechanism 32, whereby every rise on the cam 364 serves to advancethe slide 26 in relation to the base 10.

The new wheel dressing oscillator section z operated by cam 362 of theoscillator unit connects by means of a liquid column 368z with the rodend of motor 200 for retracting the wheel carriage 190. Liquid column3682 is also interrupted by a three-position pressure responsive valve380 which in the normal (cross-hatched) R0 biased position diverts theliquid column through a line 382 to the low pressure reservoir 324.Valve 380 is also connected to be shifted by pressure from the line 378through a restricted orifice-ball check cont-r01 384, for delaying thereturn motion of the valve. When shifted by the pressure of fluid fromthe line 378, the connections illustrated in the uppermost of the threerectangles are established, and the liquid column 368z directlyinterconnects t-he pulsator section z with the rod end of fluid motor200 to oscillate the wheel carriage 190. When pressure in line 378 isinterrupted to allow the valve 380 to return to its closed position, therestricted orifice 384 curtails the draining of the pressure throughline 378 and allows the connections illustrated in the middle rectangleof valve 380 to be momentarily established for the purpose of divertingfluid from the motor 200 back to the low pressure reservoir 324 throughline 382. The restricted orifice drain 384 serves the same purpose asthe momentary dwell 370 on the cam 238 of pulsator section it of themain motivator: each serves to establish briefly the connection shown inthe middle rectangle of valves 370, 380 only as they shift from theiroperative positions back to their normal (cross-hatched) positions.

Pressure in the line 378 for shifting the valves 374 and 380 isgenerated by a pump 386 which pressurizes fluid from an atmosphericreservoir 388. A two position, solenoid actuated, spring-loaded valve390 allows pressure communication from the pump 386 to the line 378 whenthe solenoid actuated connections illustrated in the uppermost rectangleare established, and allows fluid fro-m the line 378 to drain back tothe reservoir 388 when the connections illustrated in the spring-urgedor lowermost rectangle are established. A light weight ball check valve392 in the return drain line to the reservoir 388 serves to maintain thelines full of fluid and prevent air pockets from accumulating.

Fluid line 378 also communicates with connection 166 which controls thepiston 162 for shifting the limit stop of the dresser arm operatingmotor to hold the diamond point down in the operative position, aspreviously explained. Thus, when valve 390 is shifted by the solenoid toestablish the connections illustrated in the uppermost rectangle, thediamond arm 142 is held down in the operative position, the valve 374 isshifted so that undulat1ons on the cam 364 of the oscillator unit willserve by means of the ratchet mechanism 32 to advance the slide member26 in relation to the base 10 towards the grinding wheel, and valve 380is shifted to a position in which the rise and fall pattern on the cam362 of the oscillator unit is imparted to the wheel carriage .190 tooscillate the grindmg wheel to and fro in relation to the lowereddressing tool 140. When the valve .390 is spring urged to the normalposition, the pulsator sections y and z of the oscillator unit merelytransfer liquid column motionto and from the low pressure reservoir 324,and the shiftable limit stop 160 of the dresser apparatus is retractedto its normal position, whereby the diamond arm may be moved to and fromits. operative position solely by the pulsator section a of the mainmechanico-hydraulic motivator unit.

The low pressure reservoir 324 for the oscillator unit may comprise acast container 325 secured by suitable bolts 327 to the top 329 of thehousing 322 of the oscillator, and it may have a lid or cover 329 heldthereon by fasteners 331. Within a thickened portion of the base of thereservoir unit are three parallel, horizontal bores containing axiallyshiftable spools which constitute the valves 370, 374 and 380. Suitableporting connects spec1fic axial zones of the valve bores with theinterior of the reservoir; similarly, suitable porting in the manifoldplate cover 329 of the oscillator unit connects certain axial zones ofthe valve bores with the pulsator sections x, y and z; other portingfrom the biasing source R to the valve bores, from the main motivatorpulsator station It to one end of the bore for the valve 370, and fromthe line 378 to one end of the bores for the valves 374 and 380 areprovided: all such porting serves to establish the connectionsschematically illustrated in the righthand portion of FIGURE 19.

The valves 370 and 380, aside from connecting and disconnecting theliquid columns 368x and 368z to and from the lefthand end of the wheelcarriage motor 200, as explained above, also serve to simultaneouslyconnect and ,disconnect the pressurized source R0 to and from therighthand end of the motor 200. By means of this expedient, both cams atthe motivator stations g and i may present uniform dwell contours, orbase-circles, to their respective followers after moving the piston 204against the forward limit stop 216, whereupon additional vibratory oroscillatory motion imparted to the piston by either of the oscillatorcams 362 or 366 will be counter-biased by the pressurized source R0 andwill not divert fluid to the reservoir 31-2 through the relief valve 310at station 1'. When the valve 370 is shifted to establish the liquidcolumn 368x between the pulsator x and the motor 200, the valve alsocompletes a line 371 between the source RO (via the free pistonmechanism, explained below) and the motor 200 in opposition to theliquid column connection. When the valve 380 is shifted to establish theliquid column 368z between the pulsator z and the motor 200, the valvealso completes a line 381 between the source R0 (also via the freepiston mechanism) and the motor 200 in opposition to the liquid columnconnection. Thus, while the wheel carriage is shifted rapidly throughits long stroke by the preferred double-acting pulsator arrangement fromsections g and i and advantageously avoids using the relatively highpressurized return oil system, it is nevertheless shifted at a slowerrate through its shorter strokessuch as the cam 366 grind vibration orthe cam 362 dress oscillationby the single pulsator acting in oppositionto the constant pressure counter-biasing system in the same manner asthe other fluid motors on the disclosed grinding machine.

Means is also provided by this invention for isolating fluid from thesource R0 and liquid in the motor 200 to prevent air pockets or bubblesfrom migrating from the common and thus continuously agitated return oilover to the righthand portion of the motor 200 where they would impairthe positive functioning of the liquid column 3141'. This isaccomplished by use of a free piston 351 shiftable through a limitedstroke in a chamber which constitutes a portion of the fluidcommunication line between the motor 200 and the source R0. Referring toFIG- URES l7 and 19, the chamber may comprise a cylindrical bore 353east in a thickened portion of the wall 325 of the housing for thereservoir 324. A replaceable cylindrical liner or sleeve 355 is adaptedto be snugly engaged by U-cup seals 357 on the piston 351 reciprocablewithin the liner to prevent leakage past the piston. A connection 359 atthe upper end of the bore admits liquid from and to the valves 370 and380 via the lines 371 and 381, respectively; a connection 361 at thelower end of the bore admits pressurized fluid from the source R0. Thus,when either the valve 370 or the valve 380 is shifted to establish theconnections indicated in the uppermost of the diagrammatic rectangles,one or the other of the cams 362 or 366 oscillates the piston 204 of thecarriage motor 200 away from its forward limit stop 216 as the cams gand i transfer no motion to their respective liquid columns. The piston204 is oscillated against the return bias from the source R0 via thepath 361, 351, either 371 or 381 and connection 210; obviously, as themotor piston 204 is moved away from its stop 216, the free piston 351will be pushed downwardly in its bore. Similarly, as the oscillator campresents a dip or fall to its follower at either of the stations x or z,the free piston 351 will be forced upwardly in its chamber by thebiasing source R0 and will bias the motor piston 204 back to the leftmaintaining the oscillator follower in close contact with the fallingcam contour. The sealing fit of the free piston 351 in its chamber thusinhibits bubbles from the source R0 entering the lines 371, 381, andconnection 210 where they would have an undesirable compressible orspongy influence on the effectiveness of the liquid column 314: duringits subsequent operation.

Means is also provided by this invention for compensating for leakage inthe lines 371 and 381 in the vicinity of the valves 370 and 380 whichwould substract fluid therefrom with the undesirable result of allowingthe free piston 351 to reach the upper physical limit of its strokebefore the motor piston is completely returned to its limit stop 216whereupon the bottom of each dip of the oscillator cams would drawliquid into the left-hand portion of the motor 200 via the replenishingportion 308 of the balancing valve B at pulsator section g. This, ofcourse, would result in the piston 204 being walked progressivelyfarther to the right upon each minor oscillation imparted by theoscillator cam. Such a means may comprise an independent compensatingarrangement for adding a small amount of liquid to the line 371 or theline 381 prior to either of the oscillator cams taking over control ofthe motor piston 204. This addition involves movement of the free piston351 away from the upper physical limit of its stroke so that subsequentreciprocations will transfer the full biasing force from the source R tothe piston 204.

During the grind cycle oscillation which involves pulsator section x andvalve 370, the main camshaft 236 continues rotation. The compensatingmeans here comprises a small rise 363 on the cam 238 at pulsator station1' which pulses a small amount of liquid to the righthand end of themotor 200 just after the piston 204 has been eased against the limitstop 216 by the low base circle of the cam at station g, and immediatelybefore the cam at station i presents its high base circle or dwellportion to its follower. Since the piston 204 can move no farther to theleft, this small amount of liquid forces the free piston 351 away fromthe upper physical limit of its stroke against the biasing pressure fromthe source R0. The cam at station h, of course, shifts the valve 370 toestablish the connections indicated in the uppermost rectangle justprior to this; that is, immediately upon the piston 204 reaching itsstop 216 which places the grinding wheel 220 within the aperture of awork piece chucked in the holding mechanism 133. Thereafter, the grindcycle oscillatory motion imparted to the wheel carriage by the cam 366at station x will be completely counter-biased through its full retractstroke by the source R0, the free piston 351 reciprocating in time withthe motor piston 204 and preventing air or other contaminants fromentering the liquid lines of the double pulsator operated carriage motor200.

During the dressing of a new wheel cycle oscillation which involvespulsator section 2 and valve 380, the main camshaft 236 is stopped. Thecompensating means here comprises a separate motor 363 including apiston 365 reciprocable through a short stroke in a cylinder 367, andincluding a piston rod 369. The cylinder 367 is axially aligned with thecylinder 355 in which the free piston reciprocates, and the compensatorpiston 365 has a larger effective upper face area than the face areas ofthe free piston. The upper portion of the compensator cylinder connectsby means of an appropriate fluid line 361' with the source R0. The line361' is interrupted by a three-way, two position, spring loaded solenoidac tuated valve 391 which serves, in the normal spring-biased position,to interrupt communication between the cylinder 367 and the source R0and to connect the cylinder 367 with the atmospheric reservoir 388 bymeans of a line 393. Another line 395 including a one-way ball checkvalve arrangement 397 connects the upper portion of the free pistoncylinder 355 with the low pressure reservoir 324 of the oscillator unit.Thus, when the valve 391 is shifted electrically, as described below, sothat the connections indicated in the unhatched rectangle areestablished, the differential areas of the pistons 351 and 365 bothsubjected to the same pressure source R0 cause the compensator piston tomove downwardly so that its rod 369 pushes the free piston 351 away fromthe upper limit of its stroke. As the free piston is pushed down, liquidis drawn into the line 381 between the valve 330 and the free pistonthrough the check valve 397 via the line 395 from the low pressureoscillator reservoir 324. Thereafter, the dress new wheel cycleoscillatory motion imparted to the wheel carriage by the cam 362 atstation 2 will be completely counter-biased through its full retractstroke by the source R0, the free piston 351 reciprocating in time withthe motor piston 204 and preventing air or other contaminants fromentering the liquid lines of the double pulsator operated carriage motor200.

Suitable electric circuitry, not shown, including a size determiningmechanism such as limit switch 400, indicates when the grinding wheel220 reaches a prohibitively small diameter. When such a conditionexists, circuitry responsive in conventional fashion to limit switch 400stops operation of the main mechanico-hydraulic motivator cam shaft 236in a manner equivalent to pushing the cycle stop button 304. At thispoint, a light on the control panel of the grinding machine may be usedto indicate that a new grinding wheel is needed. After a new wheel isinstalled on the spindle 222, the human operator of the machine maydepress a suitable manual start button, not shown, for commencing acycle which dresses the new wheel to a desired size determined by thelimit switch 402 and to a desired surface prior to the resumption ofhigh production grinding operations. The button starts the mainmechanico-hydraulic motivator in a manner equivalent to depressing thecycle start button 302, makes a circuit through a limit switch 406 (FIG-URE 10) which senses when the wheel carriage is in its forward-mostposition, and starts an electrical timer 399 which shifts and holds thevalve 391 associated with the dress cycle free piston compensator motor.The forward position limit switch 406, when actuated, stops the mainmotivator in a manner equivalent to depressing the cycle stop button304, and actuates the solenoid for the valve 390 to hold the dressingarm down in the operative position, and to complete the liquid columnsfor pulsator sections y and 2 until the limit switch 402 is tripped.Limit switch 402 starts the main motivator in a manner equivalent todepressing the cycle start button 302, breaks the circuit through thelimit switch 406, and deactivates the solenoid for the valve 390, thusallowing regular grinding operations to proceed entirely automaticallyuntil the wheel again reaches a prohibitively small diameter.

In operation, the machine works through a repeated cycle of coordinatedmotions actuated by the cams 238 during one complete revolution of thecamshaft 236. At the beginning of each cycle, with the transmission 16in high speed, suitably designed pulsator sections, not shown, actuateloading mechanism on the tooling plate to position a work piece havingan internal surface to be ground in the work holding mechanism 133. Thecam 238 at pulsator section c will then operate mechanism to clamp thework piece in the grinding position, where it is rotated by the motor136. As soon as the work is suitably clamped for grinding, the turbinedriven internal grinding wheel 220, supported on the carriage 190, ismoved quickly forward by the motor 200 to locate the piston 204 againstthe stop 216 and the wheel within the workpiece. At this time, the fluidmotor 42 will begin to pull the parallel link supported carrier 36through a short arcuate motion (several thousandths of an inch) untilthe wheel 220 is positioned immediately adjacent the internal surface ofthe work piece.

At this point, the transmission shifts itself to low or feed speed andthe remainder of the arcuate motion of the Work carrier slide 36progresses at a slower, closely controlled rate as the wheel 220 grindsthe internal surface of the work piece in the manner desired. As soon ascontact is made between the wheel and the average work piece, pulsatorsection h shifts the valve 370 to the operative position in which theconnections illustrated in the uppermost rectangle are established. Withthe valve 370 in this position, the small rise 363' on the cam atstation i pulses a predetermined volume of liquid into the line 371 tomove the piston 351 away from the up per limit of its stroke tocompensate for any leakage from the line 371. Thereafter, the cam atsection i presents a high dwell or base circle to its follower whereuponoscillatory motion determined by the cam 366 of the oscillator unit istransferred by the liquid column 368x to the motor 200 in opposition tothe biasing pressure from the source R via lines 361, 371 to impart adesired oscillatory motion to the wheel carriage 190 and the wheel 220during thegrinding operation. During this period, the cams 238 atpulsator sections g and i present uniform dwell portions to theirfollowers so that the only motion received by the motor 200 is theadditional pulsations from the liquid column 368x. Upon completion ofthe motion of the work carrier 36 towards the grinding wheel 220, thelength of which is determined by the stroke of piston 90 in motor 42against the limit stop 102, a period of spark out is allowed in whichthe stressed members of the machine are relaxed to lighten the pressureof the high speed grinding wheel against the surface of the workpieceand obtain a highly finished, unburned surface.

Upon completion of the grinding portion of the cycle, the link supportedcarrier 36 is quickly returned along its arcuate path to its restposition determined by the limit stop 110 for the piston 90. 1 With thework thus removed from contact with the grinding wheel, the cam 238 atpulsator section h allows the valve 370 to shift to its normal position,with a momentary dwell at a position in which the excess liquid incolumn 368x is drained back through line 372 to the low pressurereservoir 324 of the oscillator unit, and the generally complementarycams at sectionsg and i no longer present dwell portions to theirfollowers but turn past their base circle portions and present risingand falling faces respectively by which the motor 200 starts to retractthe grinding wheel from the vicinity of the work piece. Whereupon, thepulsator section a moves the piston 152 to lower the diamond arm 142 tothe operative position in which the diamond point 140 is in the path ofthe periphery of the grinding wheel. Then pulsator section f actuatesthe ratchet mechanism 32 which causes the lead screw mechanism 34 topull the lower or dresser slide member 26 laterally on the machinethrough the very small distance that is desired to be dressed off thegrinding wheel. As the wheel carriage 190 continues its retractingmovement under control of the pulsator sections g and i the wheel istraversed across the newly located diamond point 140 to satisfactorilydress the wheel for the next grinding operation. The piston 152associated with pulsator section a pivots the diamond arm 142 upwardlyto the inoperative position immediately after the wheel is past and thetransmission 16 then shifts itself again to the rapid speed. Mechanismin the work piece holder 133 actuated by' pulsator section c may ungripthe work piece and ejecting mechanism operated by section e may push thework piece out of the collet where it is picked up by unloadingmechanism on the tooling plate 170 to remove the finished work piecefrom the vicinity of the grinding machine, and thus complete a normalcycle.

To maintain the accuracy of the diamond sizing dressing operation as thediamond point 140 gradually wears down through continual use, the handle120 on the compensator mechanism 108 may be turned slightly to ad- Vancethe limit stop 110. This determines the rest position, which is also thedressing position, of the link supported feed carrier 36. As thedisplacement of pistons 90 and 92 is thus shortened, surplus oil will ofcourse be needed to keep cylinder 96 and liquid column 314d full as cam238 of section d recedes to its base circle in order that the originaltiming of the feed stroke be maintained. This oil is obtained from aquantity maintained in the variable volume compensator cylinder 116, andsupplied to the liquid column line 314d at the appropriate time throughthe connection 124 by movement of the expelling 'piston 122 under timedcontrol of pulsator section b,

After many work pieces have been ground by continual rotation of themain camshaft 236, the grinding wheel 220 will be reduced to a sizewhere further grinding operations are prohibited. At this pointelectrical circuitry responsive to limit switch 400 stops the mainmotivator camshaft and allows the machine operator to install a newwheel, and reset the laterally traveling carrier 26 with the crank 46until limit switch 404 is engaged and lights a warning light. With a newwheel installed and the dresser slide 26 back on the side of the base 10away from the ratchet unit 32, the operator pushes a button (which maybe labeled dress new wheel) which starts the camshaft 236, the timer399, and closes the limit switch 406 circuit. As shaft 236 is rotated,the cams of sections g and i move the carriage 190 forward until thelimit switch 406 is tripped. This stops the camshaft and operates thesolenoid for the valve 390 to shift the pressure responsive valves 374and 380, andalso to lower and hold the diamond arm 142 in its operativeposition. With the valves 374 and 380 shifted, the free piston movedaway from the upper limit of its stroke to compensate for any leakagefrom the line 381 by previous operation of the timer controlled valve391, the cams 362 and 364 operate pulsator sections y and z to advanceincrementally the carrier 26 which moves the diamond point radiallytoward the wheel, and to impart a desired dressing oscillatory motion tothe wheel carriage 190. The timer 399 drops out as the oscillatorymotions begin and allows the valve 391 to return to its spring-urgedposition to thus render the large area compensator piston 365ineffectual. Repeated revolutions of camshaft 356 will repeatedlyoscillate the wheel away from its forward position and adjacent thedressing apparatus and also advance the dressing apparatus step by steptoward the wheel until the wheel has reached a proper size to resumegrinding operations, as indicated by limit switch 402 wihch mayinterrupt current to the solenoid of the valve 390, drop out the limitswitch 406 circuit, and also operate the cycle start button 302 when thewheel attains a satisfactory starting diameter. This operates relay 300and actuates solenoid 286 whereby the main camshaft 236 of themechanico-hydraulic motivator once again commences the cyclical grindingof work pieces throughout the useful life of the newly installedgrinding wheel, that is, until repeated advances of slides 26 undercontrol of the feeder 32 actuates the limit switch 400 once again. i

Thus, a fully automatic Wheel oscillator is provided which moves a tooland a work piece relative to one another with various length strokes'andat various rates of speed. Combined with an internal grinding machine,the high speed grinding wheel, after radially approaching the internalsurface of the work piece quite rapidly until contact is almost made andthen moving more slowly at a precisely controlled rate to produce thedesired action of the wheel on the work, is oscillated axially to andfro at a given rate. A pair of opposed pulsator units including combinedrelief and replenishing balancing valves serve to shift the wheelcarriage to and fro with one motion and without return oil. A secondpulsator unit with a valve controlled liquid column is arranged tooscillate the wheel carriage against return oil with the slower andshorter motion desired for grinding operations. Finally, a thirdpulsator unit with a valve controlled liquid column is adapted tooscillate the wheel carriage against return oil in the manner desiredfor dressing the surface of a newly installed wheel. The free pistonkeeps return oil fluid out of the double cam pulsator system, while thetwo compensator arrangements insure that the free piston does notdetract from the full-stroke counter-biasing effect of the return oilsystem when it is employed in conjunction with the oscillator cams.Suitable electric and pressure controlled valves render the entireoperation fully automatic. Because of the possibility of using flexibleconduit to confine the liquid columns, the oscillator unit of thisinvention may be located remotely from the machine, and

17. IN A MACHINE TOOL IN COMBINATION, A CARRIAGE, MEANS FOR OPERATINGTHE CARRIAGE TO-AND-FOR WITH ONE PREDETERMINED MOTION PATTERN INCLUDINGA ROTARY CAM WHICH DRIVES AN EXPANSIBLE CHAMBER TRANSMITTER CONNECTED BYA LIQUID COLUMN TO AN EXPANSIBLE CHAMBER MOTOR WHICH MOVES THE CARRIAGETO-AND-FRO, MEANS FOR OPERATING THE CARRIAGE WITH A SECOND MOTIONPATTERN INDEPENDENT OF THE FIRST MOTION PATTERN INCLUDING A SECONDROTARY CAN WHICH ACTUATES A SECOND EXPANSIBLE CHAMBER TRANSMITTERCONNECTED BY A SECOND LIQUID COLUMN TO SAID MOTOR, AND CONTROL MEANSCONNECTED TO RENDER THE SECOND CAN EFFECTIVE TO IMPART SAID SECONDMOTION PATTERN TO THE CARRIAGE AT A PREDETERMINED POINT IN THE ROTATIONOF THE FIRST CAM.